Methods for evaluating the mass of objects in motion by using a one-component strain-gauge dynamometer

We study the problems of increasing the accuracy of weight-in-motion measurements. The mass of loads in motion can be computed by using the results of measuring of unsteady forces with the help of one-component strain-gauge dynamometers. It is shown that the existing methods of dynamic weighing make it possible to measure unsteady forces with an error exceeding ~10 %. High errors of measuring the forces is explained by the fact that, as the speed of the load increases, the dependence of the accuracy of measurements of dynamic loads on the dynamic characteristics of the one-component strain-gauge dynamometers becomes more pronounced. To increase the accuracy of finding the masses, it is necessary to develop new methods for measuring forces, which exclude the systematic error caused by the dynamics of the dynamometer itself. There are two methods developed for the weight-in-motion measurements of the mass of cargo moving with high speeds over the platform of one-component strain-gauge dynamometers. The cargo weight is determined in a broad frequency range of the dynamometer, including its natural frequency. To apply the first method, the readings of the dynamometer in the vicinity of a given point of time are required to compute the first and second time derivatives of readings of the dynamometer and its dynamic coefficients obtained in laboratory conditions. To apply the second method, it is necessary to preliminarily determine the natural frequency of oscillations of the dynamometer with a platform and then the frequency of oscillations of the platform together with the moving load. Then the data of measurements obtained as a result of application of the first (or second) method are used to compute the mass of the cargo. The mean error of determination of masses by the first and the second method were equal to 2.8 % and 4.1 %, respectively. For high speeds of motion of the cargo, the error of finding the masses by both methods is close to 6.0 %. The procedure of measuring the mass of moving weights by using two proposed methods should be useful for the development of weight-measuring systems used in various branches of industry, trade, agriculture, etc.